The present invention relates to a non-light emitting or light emitting type image display device, and more particularly to an image display device, a correcting method and a correcting apparatus in which scratches on a panel glass surface in an image display section are repaired, and which are useful particularly in a thin film transistor-liquid crystal display (hereinafter abbreviated as TFT-LCD) or a plasma display panel (hereinafter abbreviated as PDP).
FIG. 1 is a schematic view showing the sectional structure of a well known TFT-LCD as a typical example of the prior art. The drawing shows three scratches 113 formed by mistake on the surface of a glass panel 106 in a display section. The scratches 113 are often observed when a manufacture apparatus contacts the glass surface in the manufacture process. Furthermore, the scratches 113 are formed particularly at locations where a glass substrate is held on a vacuum suction stage, and frequently generated by foreign matters caught between the substrate and the stage.
Environment management is performed at the manufacture site so as to reduce as much foreign matters as possible in the process, but it is impossible to completely eliminate foreign matters, so that scratches 113 on the glass surface are generated in a statistical frequency. Moreover, it is impossible to check amounts of foreign matters generated every process, and actually in many cases the presence of the scratches 113 formed on the glass surface is found for the first time in the final manufacture process of liquid crystal display panels, i.e., in the lighting inspection and whole appearance inspection performed before a polarizer 111 is applied to a liquid crystal display panel. Furthermore, back light is scattered by portions of the scratches 113, and the display quality in liquid crystal displays is frequently deteriorated to an extent which cannot be ignored.
Since such liquid crystal display panels have gone through many processes, their added value is high. Therefore, loss of resources involved in disposal of such liquid crystal display panels in this stage cannot be ignored even if such disposal is low in frequency. Therefore, from the standpoint of social request for the conservation of environment resources, it is desired to repair the glass surface scratches 113 by means of some measures.
To solve the above-described problem, the following prior art has been generally used. More specifically, when a scratch or scratches are found on a glass surface in a display section of a liquid crystal display, a method has been employed, in which abrasion of the scratch or scratches and a portion or portions around the scratch or scratches is performed until such scratch or scratches are eliminated. This method is effective for a relatively shallow scratch or scratches having a depth of several xcexcm or less, but is not entitled to be practical because such abrasion takes much time in the case of repairing a deep scratch having a depth of more than 10 xcexcm. Further, there is offered a problem that it is even difficult to repair a wide scratch as compared with the above-described scratch, for example, when a micro crack develops deeply.
On the other hand, a method of repairing that scratch which cannot be treated by way of abrasion is disclosed in Japanese Patent Unexamined Publication No. 150205/1993 or 118401/1994.
More specifically, the technique disclosed in the Japanese Patent Unexamined Publication No. 150205/1993 comprises a method of dripping a liquid organic resin having a refractive index equivalent to or on the same order of that of a material of a glass substrate onto a scratch of the display panel glass substrate with a dispenser, which mounts a needle at a tip end thereof, thermosetting the resin, abrading a surplus resin remained around the scratch with a grinder, and flatting the glass surface.
The prior art document, however, has no detailed explanation of configuration and size of the needle mounted to the tip end of the dispenser, and supply condition of the organic resin and so on, and in no way numerically describes a situation, in which the organic resin is filled inside the scratch when the repair has been completed. Therefore, a standard used in judging to what extent the scratch is repaired or whether or not the object is attained is very vague, and it is difficult to judge the effectiveness of this technique.
Moreover, like the above-described prior art, the technique described in the Japanese Patent Unexamined Publication No. 118401/1994 comprises a method of filling the scratch with a liquid organic resin having a refractive index equivalent to or on the same order of that of the panel glass material, and thermosetting the resin.
However, this technique in no way details concretely how to fill the organic resin. Furthermore, a configuration of a portion, for which the scratch is repaired, is in no way described quantitatively, and it cannot but be said that it is difficult to precisely judge the effectiveness of the technique.
The inventors of the present application actually filled an organic resin in a scratch formed on a glass surface of a liquid crystal display panel on the basis of the above-described prior art, and have found that there are involved the following many problems and that the object cannot easily be achieved.
First, with reference to FIG. 2, an explanation will be given to a method of filling a liquid organic resin into a portion with a glass scratch on a panel surface, thermosetting the resin, and shaving off a surplus resin. When it is taken into consideration that the smaller an amount of the surplus resin, the easier the disposal thereof in the event of removing the surplus resin by means of some measures, it is desirable to supply an optimum amount of the resin, conformed to a volume of the scratch as far as possible, only into the scratch. A glass scratch 202 is various in size depending upon a size of a foreign matter responsible for the scratch such that various scratches are generated including a small scratch of about 50 xcexcm and a large scratch exceeding 500 xcexcm. Furthermore, the scratch 202 has a depth in the range of several xcexcm to several tens of xcexcm, and is also various in configuration.
Here, exemplifying a rectangular parallelepiped groove of 50 xcexcm in width, 100 xcexcm in length, and 5 xcexcm in depth for the typical size of the glass scratch 202 as shown in FIG. 2A, this scratch is of 25000 xcexcm3 in volume. To precisely supply a minimum amount of resin (amounting to the volume of the scratch) into this scratch, it is essential to employ an injecting method in which an amount of the resin discharged at a time is made exceedingly small and is controllable. Concretely, it is required for the method to control the amount of the resin discharged at a time to at least 1000 to 5000 xcexcm3. Therefore, the filling of the resin into the scratch is implemented by repeating the above-described high precision discharging, and a tool capable of discharging a small amount of liquid drop is necessary in order to fill the scratch with the minimum amount of the resin.
Here, an experiment has been conducted using a micro-syringe of the smallest volume (volume of 10 xcexcL) among commercially available micro-syringes (small-sized syringes) for gas chromatography. Incidentally, this micro-syringe had a minimum graduation of 1 xcexcL and a volume corresponding to that of a rectangular parallelepiped (109 xcexcm3)with each side of 1 mm, the volume being extremely great as much as 4xc3x97104 times the volume of the above-described scratch of the typical size. More specifically, it is not possible with conventional syringes or dispensers to perform an operation of pouring the resin only into the area of the scratch 202 on a glass substrate 201. Actually, if the above-described micro-syringe is used to fill a liquid epoxy resin or the like into the scratch and the resin is then thermoset, as shown in FIG. 2B, it is only possible to supply a considerably excessive amount of the resin. In this case, the surplus resin had a difference in level, which far exceeded 150 xcexcm. Therefore, to implement injection of a filler 203 conformed to the volume of the scratch 202 and supply only an amount of the resin corresponding to the volume of the scratch 202, a technique capable of extremely minimizing an amount of the resin discharged at a time is necessary.
A second problem is the pressing necessity of a technique of removing the surplus resin, on the assumption of supplying of the relatively excessive filler 203 as described above.
For example, it is disclosed in the Japanese Patent Unexamined Publication No. 150205/1993 to remove a surplus resin by means of an abrasive and a grinder. Hereupon, the above-described small-sized micro-syringe was used to fill the resin into the scratch 202 as shown in FIG. 2A, and the resulting surplus filler having a shape shown in FIG. 2B was subjected to grinding by the grinder or cutting by a cutter, and then there was obtained the shape shown in FIG. 2C. More specifically, there was caused a problem that the filler 203 partly fell off, the filler 203 was roughed at surfaces thereof, and cut residue 204 of the resin was generated around the scratch 202. So, it was difficult to perform the working for forming a flat configuration so that the filler 203 was left only in the scratch 202.
The reason for this is that the filler 203 itself was excessive in amount and liable to fall off because of a shearing force far too great in the mechanical removal of the surplus resin, and an excessive amount of the surplus resin necessitated an enhanced cutting efficiency attributable to a coarse grain size of a grinder wheel, resulting in an increase in roughness of the processed surface. Also, it is problematic that a new cleaning process must be added to remove cuttings and shavings generated by the cutting and grinding processes.
It is desirable to dispense with the cutting and grinding processes, which accompany the repairing of scratch or scratches, and it is necessary to develop a method of reducing a surplus filler as far as possible so that a simple processing suffices even when the cutting and grinding processes are executed. Thus, to facilitate the process of removing the surplus filler, it is desirable that the method comprises supplying an amount of the filler 203 corresponding to the volume of the scratch 202 with good precision. More desirably, an ultra-high precision filling method is used to supply the filler 203 only into the scratch 202 to permit the resin to be cured with some measures, which will not do any damage to the entire image display device, such curing ideally making the surface of the filler 203 substantially flush with the glass surface around the scratch 202 for completion of the repair and doing away with any mechanical working.
A third problem is the positioning of the filler in the injecting process. Since scratch varies in size from several tens of xcexcm to about several hundreds of xcexcm, the scratch itself can be recognized with the naked eye. However, in order to inject the filler only into an area of the scratch 202 with good precision, it is impossible to attain the object by visually determining a position, to which the filler should be discharged and manually performing the work, and so it is necessary to exactly position a tip end of a filler discharge unit (e.g., the above-described micro-syringe) right above the scratch 202 at least in the field of view of a substantial microscope or an optical microscope.
Regrettably, the above-described prior documents in no way describe the necessity of the positioning operation indispensable for attaining the object. Moreover, even assuming that the accurate positioning has been effected as described above, the problem concerning the removal of the surplus filler cannot be solved with the discharge performance of the micro-syringe as described above.
A fourth problem is that, in order to repair the glass scratch 202 in the production site with good reproducibility, an appropriate method of quantitative evaluation for configuration of the scratch as restored is needed, and this problem will be described hereinafter.
Assuming that the method of precisely filling/restoring a scratch or scratches can be developed to solve the above-described problems, considerations will be given to those conditions, which configuration of a scratch or scratches as restored should meet.
First, repair of a scratch is defined by the fact xe2x80x9cthe scratch is filled with an appropriate filler to present an appropriate configuration and is finished to produce a state, in which the existence of the scratch cannot be visually recognized any morexe2x80x9d. The cause to offer a problem in terms of display that a scratch or scratches are visually recognized will be investigated in details with reference to FIGS. 3 and 4 in the case where a scratch or scratches are existent on a display panel glass surface of a TFT-LCD representative of an active matrix drive type display.
With the TFT-LCD, light entering human eyes is classified into two types, that is, light passing through an opening of the TFT-LCD from a light source being back light, and a reflected light resulting from an ambient light being reflected by the surface of the display panel. Even if repair of a scratch or scratches is incomplete, cut-off of either of optical paths of the both lights is visually perceived for recognition of the presence of the scratch or scratches.
First, in the case shown in FIG. 3, a scratch on a glass substrate 301 is accurately filled with a filler 302 having a refractive index equivalent to or on the same order of that of the glass and having substantially the same amount as a volume of the scratch, and the scratch is repaired such that a surface of the filler 302 is made substantially flush with a surface of the glass substrate 301 and has substantially the same smoothness of that of the surface of filler 302. In this case, light 303 from a back light proceeds along a normal optical path in a portion, in which the scratch is repaired, without any interference. Moreover, an ambient light 304 does not behave on the surface of the filler 302 and on the surface of the glass substrate 301 significantly differently, and an edge of the filler 302 is also contiguous to the glass in substantially the same flat surface, so that the scratch itself forms no specific point in terms of visual perception. Therefore, the scratch is completely repaired and is not visually perceived, and it can be said that ideal repair of the scratch can be realized.
On the other hand, in the case shown in FIG. 4, an amount of a filler 402 as filled slightly exceeds a volume of a scratch, and a part of the filler 402 is formed to slightly protrude outside of an edge of the scratch. Since a scratch is various in size and configuration, slightly excessive filling can practically occur even with the use of a high-precision filling method. Therefore, for the repaired configuration as shown in FIG. 4, it is important as a practical issue to establish a standard for clearly prescribing configurational limitations which cannot be visually perceived.
In addition, the case as illustrated in FIG. 4 is taken into consideration, in which the surface of the filler is substantially flat over a large part of a portion, in which the scratch is repaired, except the edge of the filler 402, and the filler 402 and the glass substrate 401 substantially coincide in refractive index with each other. In this case, the back light (1) 405 is in no way modulated at the interfaces of glass/filler and filler/air, and so advances along a normal path. Therefore, the scratch is not perceived in this area. Also, the ambient light (1) 406 is similarly free of interference on the optical path in this area, and the scratch is not perceived in this area.
However, the situation differs in the edge of the filler 402. First, when the back light (2) 407 enters an edge of the filler 402 (right edge of FIG. 4), a part of light 407 is partially reflected (408) at the interface of filler/air in a left downward direction, and at the same time the remaining light advances as an abnormal transmission light 409 in a direction offset from a straight advancing direction. Therefore, luminance distribution changes in this area, and the edge of the filler 402 is visually perceived by a user who observes the image display device.
Subsequently, in the case where the ambient light (2) 410 is incident upon the edge of the filler 402 (e.g., a left edge of FIG. 4), it branches into a reflected light 411 and a refracted light 412 at the interface of air/filler in the same manner as described above, and the both lights advance in a direction offset from a direction of incidence. Therefore, luminance distribution changes also in this area, which is visually perceived by the user. Actually, the back light 407 and ambient light 410 are modulated in an entire outer periphery, defined by the edge of the filler 402, so that the entire filler 402 is visually perceived.
In addition, the above-described phenomenon can be discussed in the same manner, in the case where the filler is slightly insufficient, for example, in the case where a surface of a filler 1202 is shaped to be slightly lower than a surface of a glass substrate 1201 as shown in FIG. 5, which will be described later. As a result, the edge of the filler 1202 is visually perceived. (Since the principle can easily be understood from the above description, the detailed description thereof is omitted.)
Furthermore, the phenomenon of modulation, which the back light and the ambient light experience, depends on tapered angles of the fillers 402 and 1202 (404 on the left edge in FIG. 4, and 1204 on the left edge in FIG. 5). More specifically, the phenomenon of modulation becomes insignificant as the tapered angles become smaller, with the result that the edge of the filler changes less in luminance change, which makes visual perception difficult. In other words, the smaller the tapered angles are, the less conspicuous the portion, in which the scratch is repaired, becomes, so that it becomes significantly meaningful to determine an optimum value of the tapered angle of the edge of the filler.
The above-described prior-art problems will be put in order and described hereinafter.
The present invention provides an image display device, typified by TFT-LCD, in which a scratch or scratches on a glass surface of an image display panel is filled with a filler having a refractive index equivalent to or on the same order of that of glass, and repaired by:
(1) performing accurate positioning for filling into an area or areas in which the scratch or scratches are present;
(2) injecting an amount of the liquid filler corresponding to the volume of the scratch or scratches only into the area or areas, in which the scratch or scratches are present, and curing the filler; and
(3) desirably using a means for finishing a configuration, in which a filler surface and a glass surface around the scratch or scratches become substantially flush with each other, to repair the scratch or scratches, and the invention provides such means.
(4) Also, the invention provides a means for applying a slight-degree precision abrasion as desired, even when the filler becomes slightly surplus (protrudes from the scratch or scratches) or insufficient for an area or areas, in which the scratch or scratches are existent, to finish an edge of the area, into which the filler is, into a tapered configuration, which cannot be visually perceived, and also an image display device, which uses such means to realize repair of a scratch or scratches.
First, in order to repair the above-described scratch on the glass surface with high precision, a technique of supplying a liquid material only to an optional minute area on the glass surface is needed. This subject can be solved by using, for example, a micro-injection apparatus disclosed in Japanese Patent Unexamined Publication No. 8514/1996, and using a method shown in FIGS. 6A to 6D. More specifically, the apparatus is used for filling a liquid filler 504 into a pipette 503 molded to have a tip end inner diameter of 1 to 10 xcexcm, supplying an inert gas into the pipette from the other end thereof, and injecting a minute amount of the liquid material via the tip end of the pipette 503.
Concretely, a discharge port of the pipette 503 filled with the liquid filler 504 is positioned right above the scratch 502 (FIG. 6A), and the pipette 503 is lowered with its inclination kept constant to be placed in contact with the scratch 502 of a glass substrate 501 (FIG. 6B). Subsequently, a nitrogen gas 505 is supplied into the pipette 503 from behind in a pulsed manner, and the liquid filler 504 is discharged via the pipette tip end (FIG. 6C). In addition, the above-described operation is implemented in the existence of a microscope, and the pipette 503 is quickly raised from the glass substrate 501 every discharge so that the filling state in the scratch 502 is confirmed (FIG. 6D). Furthermore, when an amount of filling is insufficient, the liquid material is repeatedly discharged and the discharging is completed when it is judged the scratch 502 is completely filled with the liquid filler 504.
Here, when an amount of the liquid filler 504 discharged at a time is to be changed, it suffices to change the pressure of the nitrogen gas 505 or the pulse application time. Thereby, it becomes possible to optimize an amount of discharge of the liquid filler corresponding to a size of the scratch to perform injection of the filler with high precision.
And, the implementation of the above-described concept and the solving of the above-described problems in (1), (2) and (3) can be attained by an automatic liquid material supply apparatus provided with (a) a mechanism for mounting on a stage a liquid crystal display panel with a scratch or scratches to position the same, (b) a mechanism for observation of a surface of the liquid crystal display panel, (c) a mechanism for operating the pipette filled with the liquid material to position the same, and (d) a mechanism for supplying an inert gas to the pipette from behind in a pulsed manner to discharge the liquid material.
Concretely, after the pipette 503 molded to have the tip end inner diameter of 1 to 10 xcexcm is filled with epoxy resin, the pipette is held, and its tip end is placed at a center of visual field in an optical observation system. Thereafter, the pipette 503 is lowered, and contact between the pipette 503 and the substrate 501 is sensed based on a state, in which the pipette tip end displaces on the surface of the substrate 501. Subsequently, the nitrogen gas 505 having, for example, a pressure of 150 kPa is supplied from behind the pipette 503 in a pulse of 50 msec in width. At this time, the tip end of the pipette 503 contacts the substrate 501 at an angle of 30 to 45xc2x0, and supplying of nitrogen in a pulsed manner causes the liquid material 504 in the pipette to be discharged from the tip end of the pipette 503 with a resolution of about 1 pL at minimum. Subsequently, after completion of supplying of the nitrogen, for example, 100 msec, the pipette 503 is raised, and the pipette tip end is separated from the substrate 501, whereby it is possible to control an amount of the liquid material supplied with high precision. Incidentally, FIG. 7 shows a relationship between the number of times, in which nitrogen is supplied from behind the pipette in a pulsed manner, and an amount of the liquid material supplied, both being related to each other in a substantially proportional manner.
Finally, it goes on to curing treatment of the filler after the injection of the liquid filler. In the curing treatment, it is necessary to select the optimum condition depending upon properties of the material used, while it is possible to employ thermosetting or photo-setting on the assumption that the liquid crystal display is not damaged. As the liquid filler, a thermosetting type epoxy resin, a thermosetting type acrylic resin, a photo-setting resin, and the like can be used. It is essential that the liquid filler have a refractive index equivalent to or on the same order of that of glass used in the liquid crystal display, the liquid filler is colorless and transparent, and that the liquid filler has a high adhesion to the glass.
In addition, with the above-described micro-injection method, supplying of the liquid filler of an amount corresponding to a volume of most of scratches on the glass can be performed highly precisely, but slightly surplus filling sometimes occurs in the event of a relatively small volume of the scratch. In such case, it goes without saying that a favorable configuration of a filled portion can be obtained by, for example, using a tape grinding apparatus to grind and remove the raised portion of the surplus filler.
An important knowledge obtained by the inventors through the experiments reveals that, even when the panel surface and the filler surface fail to become perfectly flush with each other, the scratch on the glass surface cannot be visually perceived if a difference in level therebetween is within a range of xc2x15.0 xcexcm, and a tapered angle formed between the panel surface and the end of the liquid material is 45 degrees or less, preferably ten degrees or less. Of course the reason for this is due to a physical reason that the difference in level between the panel surface and the filler surface, or the tapered angle formed between the panel surface and the end of the liquid material edge is small, but that, when the TFT-LCD is assembled, a polarizer is attached to the repaired glass plate via an adhesive layer of, for example, about 25 xcexcm in thickness, to permit the adhesive layer to physically accommodate the difference in level of xc2x15.0 xcexcm and to fit the tapered surface to function as an optical member for substantially eliminating the tapered surface.